Hi Newkirk,
 
Thanks for the reply.  My colleague solved the problem. 
 
Since the cDQA-9188 is an Ethernet Device, I need to "reserve" it first.  The steps are as follows:
1. In NI MAX (software on the desktop), select the rack [My System -> Devices and Interfaces -> Network Devices -> NI cDAQ-9188]
2. Select ‘Reserve Chassis’ tab.
 
This way, the cards within the rack shows up in NI MAX and NI SignalExpress.
 
Thanks all for helping.